300SE1993

Hi all! I test drove a 2012 S350 Bluetec yesterday and was very surprised to note smoke out the tailpipe on hard acceleration. It was actually worse than the '80s turbodiesels I've driven in the past. You could say it was "rolling coal". I know from owning multiple modern diesels it's not supposed to do that. it did it every time, even after about a 20 minute test drive. I searched the forum, but really don't see anything that references this. One theory was that the car was in an active regen, but even if that was the case, I still would not expect smoke like that.

Another noted item is that there is an exhaust leak somewhere under the hood. Very strong diesel smoke smell coming from somewhere. Car was exclusively dealer maintained from what I can tell and is presently close to 140K miles range.

Any thoughts on what might cause it to "roll coal"? Am I looking at a new DPF? Something else?

kajtek1

Those engines do not produce smoke at all. Obviously I am not behind me when I stomp on gas pedal, but I observe the mirrors and there is nothing I could see. DPF is not making difference on smoking.
You did not say what mileage, but I would rather suspect bad injectors.
Did you run car scan?

peter2772000

Or a complete lack of a DPF along with the leaky injectors? I would think that if he has a functioning DPF, it won't last long with all that particulate passing thru it.
I bypassed my DPF completely and I haven't seen any smoke in my mirrors either.

300SE1993

I forgot my scanner when I went to look at it. The dealer found a few other things wrong with it like oil leaks and torn CV boots. This may very well be one to walk away from unless it's extremely cheap.

kajtek1

Considering value of 2012, sounds like beaten-up car, the set of new plugs will cost close to it. .